Well, I looked it up and you have a 921 bulb. I just bought these bulbs:
http://www.ebay.com/itm/2pcs-921-91...Parts_Accessories&vxp=mtr&hash=item3cc028baf9
Let me just say .. WOAH! I bought them for my cargo lamps so when I get tailgaters they will back off immediately! muahaha
Some say those bulbs are just like having reverse HIDs as some people do.
Also, here is your bulb guide for future reference ..
2008 DODGE Ram Pickup
High & low beam headlamp
H13 (9008)
H13ST SilverStar: The brighter and whiter light. Up to 35% brighter, up to 30% more downroad visibility and up to 35% more sideroad visibility.
H13XV XtraVision: The brighter light for upgraded performance. Up to 30% brighter light and up to 25% more downroad visibility.
Parking light
3157A
3157NALL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Front turn signal
3157A
3157NALL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Rear turn signal
3157
3157ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
3157LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Tail light
3157
3157ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
3157LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Stop light
3157
3157ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
3157LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
High mount stop light
912
912LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Fog/Driving light
9006
9006SU SilverStar Ultra: The brightest and whitest light. Up to 50% brighter, up to 40% more downroad visibility and up to 50% more sideroad visibility.
9006ST SilverStar: The brighter and whiter light. Up to 35% brighter, up to 30% more downroad visibility and up to 35% more sideroad visibility.
9006EB EcoBright - Your Environmental Choice. Save Energy - Save Money. Up to 25% brighter light. CO2 reduced 9 to 21%. Gas savings $2 to $19.
9006XV XtraVision: The brighter light for upgraded performance. Up to 30% brighter light and up to 25% more downroad visibility.
9006CB Cool Blue: The whiter light for style. Up to 25% brighter light and up to 25% more downroad visibility.
License plate
168
168ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
168LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Back up light
921
921ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
921LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Front sidemarker
2825
2825ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
2825LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Glove box
194
194ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
194LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Map light
194
194ST SilverStar: The brighter, whiter signal light. Up to 30% brighter light, up to 20% whiter light and up to 10% farther and wider.
194LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
212-2
212-2LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Dome light
578
578LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Step/Courtesy light
37
37LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Trunk/Cargo area
912
912LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.
Under hood light
561
561LL SYLVANIA Long Life miniature bulbs perform twice as long as any standard miniature bulb. Designed for durability, lower maintenance and greater safety.